class Sum
{
public:
    Sum()
    {
        _sum += _n;
        ++_n;
    }

    static int GetRet()
    {
        return _sum;
    }
private:
    static int _sum;
    static int _n;
};

int Sum::_sum = 0;
int Sum::_n = 1;

class Solution {
public:
    int Sum_Solution(int n) {
        Sum arr[n];

        return Sum::GetRet();
    }
};